JP2009173793A - Diene rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diene rubber composition suitable e.g. as a vulcanizing molding material of a reinforcing liner layer having a crescent cross-section and placed at the inner side of carcass layers of the right and left sidewalls of a run flat tire, and enabling the improvement in the run flat durability by suppressing the increase of heat-generation without lowering the storage elastic modulus. <P>SOLUTION: The diene rubber composition is produced by compounding (a) 100 pts.wt. of a diene rubber containing 20-40 pts.wt. of natural rubber and 40-80 pts.wt. of a polybutadiene rubber with (b) 30-70 pts.wt. of carbon black, (c) 30-70 pts.wt. of crushed bituminous coal and (d) 5-8 pts.wt. of sulfur. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a diene rubber composition. More specifically, the present invention relates to a diene rubber composition that is suitably used as a vulcanization molding material for a reinforcing liner layer having a crescent-shaped cross section disposed inside the carcass layer of left and right sidewall portions of a run flat tire.

Conventionally, when the internal pressure of a pneumatic tire suddenly drops due to puncture, burst, etc., the crescent cross-section is reinforced inside the carcass layer on the side wall to provide run-flatness that enables a certain distance of travel. A tire (run flat tire) with a liner inserted is used. In order to improve the run flatness, it is necessary to make the reinforcing liner layer highly elastic, and generally a large amount of carbon black is blended. However, a large amount of carbon black compounded increases the heat generation in the side wall part with large deformation, and as a result, the rubber breaks down and causes failure. There was a limit to the improvement in mileage.
JP 2002-155169 A

  An object of the present invention is to improve run flat durability by suppressing an increase in calorific value without lowering storage elastic modulus, inside the carcass layer inside the left and right sidewall portions of the run flat tire, respectively. An object of the present invention is to provide a diene rubber composition that is suitably used as a vulcanization molding material or the like for a reinforcing liner layer having a crescent-shaped cross section.

  The object of the present invention is (a) 100 parts by weight of a diene rubber containing 20 to 40 parts by weight of natural rubber and 40 to 80 parts by weight of polybutadiene rubber, and (b) 30 to 70 parts by weight of carbon black, (c It is achieved by a diene rubber composition comprising 30) to 70 parts by weight of bituminous coal pulverized product and 5 to 8 parts by weight of sulfur.

  The diene rubber composition according to the present invention improves the run flat durability by suppressing the increase in calorific value without reducing the storage elastic modulus of the vulcanized product. It is suitably used as a vulcanization molding material for a reinforcing liner layer having a crescent-shaped cross section disposed inside the carcass layer.

  As the diene rubber of component (a), those containing 20 to 40 parts by weight of natural rubber (NR) and 40 to 80 parts by weight of polybutadiene rubber (BR) are used. In addition, if it is 40 parts by weight or less, cis-1,4-polybutadiene modified with syndiotactic-1,2-polybutadiene (vinyl cis rubber: VCR), chloroprene rubber (CR), butyl rubber (IIR), nitrile rubber (NBR), styrene-butadiene rubber (SBR), ethylene-propylene-diene copolymer rubber (EPDM), styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, etc. A diene rubber, preferably VCR, can also be used as a blend rubber. Here, as the VCR, commercially available products such as UBE products UBEPOL-VCR412, UBEPOL-VCR617, UBEPOL-VCR450, UBEPOL-VCR800 and the like can be used as they are. If natural rubber is used outside the above range, the heat build-up will deteriorate and the run-flat durability will be inferior. On the other hand, if polybutadiene rubber is used in a smaller proportion, the heat-generation will deteriorate and the run flat will be deteriorated. It becomes inferior in durability.

  Component (b), carbon black, is used in such a proportion that it is 30 to 70 parts by weight or more, preferably 35 to 60 parts by weight per 100 parts by weight of the diene rubber. If carbon black is used at a lower ratio, the storage elastic modulus decreases and run flat durability deteriorates. On the other hand, if it is used at a higher ratio, heat generation deteriorates and run flat durability is deteriorated. Become inferior. As the carbon black, FEF, GPF grades and the like are used.

  (c) Component bituminous coal or non-caking coal bituminous coal pulverized material is an average of coal containing bituminous coal (B1, B2, C in JIS M1002 coal classification) which is a kind of coal and called high-grade coal Particle size (according to ASTM D1511; measured using average measuring instrument Microtrac SRA 150) About 0.01-100 μm, preferably about 0.05-50 μm, with specific gravity of 1.6 or less, preferably 1.35 or less It is done.

  The bituminous coal pulverized product is used in a proportion of 30 to 70 parts by weight, preferably 35 to 60 parts by weight per 100 parts by weight of the diene rubber. When the blending ratio of the bituminous coal pulverized product is less than this, it becomes impossible to satisfy the low exothermic property. On the other hand, when the blending ratio is larger than this, the breaking characteristics are lowered.

  The sulfur component (d) is used in a proportion of 5 to 8 parts by weight, preferably 5 to 7 parts by weight, per 100 parts by weight of the diene rubber. If sulfur is used in a smaller ratio, the exothermic property will be deteriorated. On the other hand, if it is used in a higher ratio, the breaking strength will be lowered, which is not preferable.

  In the diene rubber composition containing the above components as essential components, compounding agents generally used as rubber compounding agents, for example, thiazole, sulfenamide, guanidine, thiuram and the like are added. Sulfur accelerators, reinforcing agents or fillers such as talc, clay, graphite, calcium silicate, processing aids such as stearic acid, paraffin wax, aroma oil, zinc oxide, anti-aging agents, plasticizers, etc. as appropriate Used in combination.

  The composition was prepared by kneading by a general method using a kneader such as a kneader, a Banbury mixer, and an open roll, and the obtained composition was a diene rubber, a vulcanizing agent, Vulcanized at a vulcanization temperature in accordance with the type of vulcanization accelerator and the blending ratio thereof, and inside the carcass layer 4 located on the left and right sidewall portions 2 of the run-flat tire shown in FIG. The arranged crescent-shaped reinforcing liner layer 6 is formed.

  Next, the present invention will be described with reference to examples.

Example 1
Natural rubber (STR20) 30 parts by weight Polybutadiene rubber (Nippon ZEON product Nipol BR1220) 70 〃
Carbon black (Tokai carbon product seast SOP) 30 〃
Bituminous coal (Austin Black 325; 55 製品, Coal Fillers Incorporated)
(Average particle size 5.50μm, specific gravity 1.31)
Sulfur (Shikoku Kasei Kogyo Product Muclon OT-20; sulfur content 80%) 6.3 〃
(Sulfur amount 5.0 〃)
Vulcanization accelerator (Sanshin Chemical Industry Sunseller NS-G) 2.5 〃
Zinc oxide (Zondox Chemical Products Zinc Oxide 3 types) 3
Stearic acid (Japanese fat product beads stearic acid YR) 1 〃
Anti-aging agent (Seiko Chemical Product Ozonon 6C) 1 〃

  Among the above components, the components other than the vulcanization accelerator and sulfur were kneaded for 5 minutes with a 1.5 L closed mixer and released when the temperature reached 160 ° C. to obtain a master batch. A vulcanization accelerator and sulfur were added to this master batch and kneaded with an open roll to obtain a diene rubber composition.

Example 2
In Example 1, the amount of polybutadiene rubber was changed to 40 parts by weight, and 30 parts by weight of cis-1,4-polybutadiene (Ube Industries UBEPOL-VCR412) modified with syndiotactic-1,2-polybutadiene was used. It was.

Example 3
In Example 1, the amount of natural rubber was changed to 20 parts by weight, the amount of polybutadiene rubber was changed to 40 parts by weight, and cis-1,4-polybutadiene modified with syndiotactic-1,2-polybutadiene (UBEPOL- VCR412) 40 parts by weight were used.

Example 4
In Example 1, a diene rubber composition comprising the following components was used.
Natural rubber (STR20) 20 parts by weight Polybutadiene rubber (Nipol BR1220) 40 〃
40〃 modified with syndiotactic-1,2-polybutadiene
Cis-1,4-polybutadiene (UBEPOL-VCR412)
Carbon black (Seast SOP) 40 〃
Bituminous coal (Austin Black 325; Coal Fillers Incorporated product 45 〃)
(Average particle size 5.50μm, specific gravity 1.31)
Sulfur (Muclon OT-20; sulfur content 80%) 10 〃
(Sulfur content 8 〃)
Vulcanization accelerator (Sunseller NS-G) 2.5 〃
Zinc oxide (3 types of zinc oxide) 3 〃
Stearic acid (bead stearic acid YR) 1 〃
Anti-aging agent (Ozonon 6C) 1 〃

Comparative example 1 (standard example)
In Example 1, the bituminous coal pulverized product was not used, and the carbon black content was changed to 60 parts by weight.

Comparative Example 2
In Example 1, sulfur was changed to 5 parts by weight (4 parts by weight of sulfur) and used.

Comparative Example 3
In Example 1, the carbon black amount was changed to 65 parts by weight, and the bituminous coal pulverized material amount was changed to 20 parts by weight.

Comparative Example 4
In Example 1, the amount of polybutadiene rubber was changed to 30 parts by weight, and 40 parts by weight of cis-1,4-polybutadiene (UBEPOL-VCR412) modified with syndiotactic-1,2-polybutadiene was used.

Comparative Example 5
In Example 1, the amount of natural rubber was changed to 10 parts by weight, the amount of polybutadiene rubber was changed to 50 parts by weight, and cis-1,4-polybutadiene modified with syndiotactic-1,2-polybutadiene (UBEPOL-VCR412) 40 parts by weight were used.

Comparative Example 6
In Example 1, the amount of natural rubber was changed to 50 parts by weight, and the amount of polybutadiene rubber was changed to 50 parts by weight.

Comparative Example 7
In Example 1, the carbon black amount was changed to 20 parts by weight, and the bituminous coal pulverized material amount was changed to 70 parts by weight.

Comparative Example 8
In Example 1, the carbon black amount was changed to 80 parts by weight.

About the vulcanized rubber sheet obtained by vulcanizing the diene rubber composition obtained in each of the above Examples and Comparative Examples at 160 ° C. for 20 minutes to obtain a vulcanized rubber sheet (15 × 15 × 0.2 cm) The following items were measured.
Storage elastic modulus (E ') and loss tangent (tan δ): Using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho, ± 2% dynamic strain at a frequency of 20Hz with 10% elongation strain applied as static strain at 60 ° C Run-flat durability measured by applying to: 3.8kN / measurement distance until a tire breaks down with a test tire attached to a vehicle with a tire load so that the tire does not fall off the rim at an air pressure of 0kPa The value obtained in the standard example is shown as an index of 100 (the larger the value, the better the run flat durability)

The results obtained are shown in the following table.
table

Example storage elastic modulus E ′ loss tangent tan δ run flat durability Example 1 12.1 0.05 103
〃 2 13.2 0.06 103
３ 3 13.1 0.06 104
４ 4 13.6 0.05 105
Comparative Example 1 12.3 0.08 100
〃 2 11.4 0.08 99
３ 3 12.4 0.09 96
４ 4 12.3 0.07 95
５ 5 11.1 0.07 97
６ 6 12.3 0.10 92
７ 7 10.1 0.06 92
８ 8 14.2 0.10 92

From the above results, the following can be said.
(1) In each example, by using a predetermined amount of bituminous coal pulverized material and carbon black, it is possible to achieve a reduction in loss tangent without reducing storage elastic modulus, and excellent run-flat durability.
(2) Even if cis-1,4-polybutadiene modified with syndiotactic-1,2-polybutadiene is added, excellent run flat if each of the components (a) to (d) is within the specified range. Shows durability.
(3) Addition of sulfur in an amount of 8 parts by weight with respect to 100 parts by weight of diene rubber achieves a reduction in loss tangent and exhibits excellent run-flat durability.
(4) When the amount of sulfur is small, the loss tangent tan δ is 0.06 or more (Comparative Example 2).
(5) If the amount of bituminous coal pulverized material is small, the loss tangent tan δ is 0.06 or more and the run-flat durability is also deteriorated (Comparative Example 3).
(6) If the amount of polybutadiene rubber is small, even if it is supplemented with cis-1,4-polybutadiene modified with syndiotactic-1,2-polybutadiene, the loss tangent tanδ will be 0.06 or more, and run flat Durability is also deteriorated (Comparative Example 4).
(7) When the amount of natural rubber is small, the loss tangent tan δ is 0.06 or more, and the run-flat durability is also deteriorated (Comparative Example 5).
(8) When the amount of natural rubber is large, loss tangent is high and run-flat durability is deteriorated (Comparative Example 6).
(9) When the amount of carbon black is small, the storage elastic modulus is lowered and the run-flat durability is deteriorated (Comparative Example 7).
(10) When the amount of carbon black is large, loss tangent is high and run-flat durability is deteriorated (Comparative Example 8).

It is principal part sectional drawing of a run flat tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Reinforcement liner layer of a crescent-shaped cross section

Claims (5)

  (b) 30 to 70 parts by weight of carbon black and (c) 30 to 70 parts of bituminous coal pulverized product with respect to 100 parts by weight of diene rubber including 20 to 40 parts by weight of natural rubber and 40 to 80 parts by weight of polybutadiene rubber A diene rubber composition comprising 5 parts by weight and (d) 5 to 8 parts by weight of sulfur.   (a) Diene rubber containing 20 to 40 parts by weight of natural rubber, 40 to 80 parts by weight of polybutadiene rubber and 40 parts by weight or less of cis-1,4-polybutadiene modified with syndiotactic-1,2-polybutadiene as component (a) The diene rubber composition according to claim 1, wherein 100 parts by weight is used.   The diene rubber composition according to claim 1 or 2, which gives a vulcanizate having a loss tangent (tan δ) at 60 ° C of 0.06 or less.   3. The diene rubber composition according to claim 1, wherein the diene rubber composition is used as a vulcanization molding material for a reinforcing liner layer having a crescent-shaped cross section disposed inside the carcass layer in the left and right sidewall portions of the run flat tire.   A run flat tire having a reinforcing liner layer having a crescent cross section formed by vulcanization molding from the diene rubber composition according to claim 4.

Images